1919\u0031\u0039 (C99)\U000031\U000039 (C99)\x31\x39 (encoding-dependent)\061\071 (encoding-dependent)\u{31}\u{39} (C++23)\x{31}\x{39} (C++23, encoding-dependent)\o{061}\o{071} (C++23, encoding-dependent)\U00000031\U00000039\u0031\u0039\x31\x39 (encoding-dependent)\061\071 (encoding-dependent)\u0031\u0039\u{31}\u{39}\u0031\u0039\x31\x39\31\39\000031\000039=31=39%31%39